Method and means for measuring and recording interval demand for apparent power



A ril 23, 1935. A D. DU BOIS METHOD AND MEANS FOR MEASURING AND REOORDINGY INTERVAL DEMAND FOR APPARENT POWER Filed Sept. 22, 1930 4 Patented Apr. 23, 1935 1,998,711 7 METHOD AND MEANS FOR MEASURING AND RECORDING INTERVAL DEMAND FOR, APPARENT POWER Alexander Dawes Du Bois', Excelsior, Minn. Application September 22, 1930, Serial No. 483,591

18 Claims.

I This invention relates to measurements in alternating-current electric circuits; and more partlcularly to measurements in power' circuits or systems in which the current may be out of phase with the pressure. The present invention is a continuation in part of the invention set forth in iigyfpplication, Serial No. 205,598, filed July 14,

A primary object of the invention is to provide an improved and simplified method of determining the apparent-power demand (commonly referred to as the kilovolt-ampere demand) of a user of electric power. In practice it is very desirable to measure and record the apparentpower demand, as this is one of the important factors of the cost of generating and supplying electric power. I

Further objects of the invention area-to provide method and meansior measuring and printing on a record sheet the separate, successive interval demands for apparent power (kv-.-a.) during any number of time intervals; to provide method and means for printing in the same record the successive efiective' power demands (lav/J for the same time intervals; to provide method and means for registeringthe maximum of all the interval demands for apparent power occurring within a total billing period; to provide method and means for registering the maxof all interval demands for effective power occurring within the total billing period; to provide improved means for automatically forwarding and retracting a pair of traversing members in response to energy meters: and ati'ming'me'cha- 1115111; to provide means for insuring complete retraction of both traversing members; to provide improved means for quickly disengaging the traversing members fromv their propelling devices in response to ti ing means,v andfor quickly engaging them m: response to the retracted traversing members andv to providc'other 'mprovemen-ts accessory to these objects as herein setfo'rth. The

invention provides for retention oi the usualfunctions of two standard meters employed in the method, :yto register total effective energy (kw-hrs.) 'andtotal reactive energy (react-lav.- a-.-l'1rs used during a billing period. Moreover the powei factor foreach successive time interval.

can easily derived from the recorded interval demands for apparent power and effiective power;

I accomplish these objects as hereinafter de-' scribed, and illustrated in the accompanying drawing to which reference is hereby made. and in which f Fig.1 is. a diagram illustratmg thegeometrical relations employed .in my invention, and show ing the relative paths of travel of two traversing elements; I

Fig. 2 is a diagram of typical means for performing, the method;

Fig. 3 is adiagrammatic representation 01 a, complete automatic apparatus;

Fig. 4 is an end elevation of certain parts of the mechanism as viewed from line 4, 4', of 3;

Fig. 5 is an enlarged diagrammatic: detail partly in section on the line 5, of Fig. 3;. and

Fig. 6 is a diagrammatic detail showing. an alternative form of traversing. gear and. means for disengagement.

Similar: reference letters and numerals refer to similar parts throughout the several views.

It is known, to persons skilled in the art to which this invention appertains, that the appare ent-energy deliveredin a given time'is the geotional toithe reactive power in. the; circuit under consideration, the distance 0A traveled by the element in a given time will be a measure ofthe reactive energy for that time. Likewise, ifa sec' ond traversing element be simultaneously moved from 0 toward; B, with a velocity proportionalv to u the efiective power in the circuit, the distance OB traveledby this element,..in the same time interval, will be a measure of the eifective energy for thetimeinterval. Hence the lengthAB of the hypotenuse of the right triangle formed in the manner described, is a measure of. the total apparent energy for the predetermined time interval. This quantity when divided by the time of the interval gives the apparent rate of flow of emergy, which is apparent power. If the measur-. ing scale, applied. to the hypotenuse, is appropriately calibrated with reference tothe time interval, the measurement of AB will directly show the mean apparent'power for-the interval;

This quantity will be referred to as the interval. L

demand. Itwillbe commonly measuredinvoitamperes of in kilovolt-amperes; The angle: ABO, between hypotenuse and base of. the triangle of energy, is the mean.angle-ofphasedisplacement between pressure and current the circuit; hence.

the cosine of this angle is the mean power-factor f the load during the time interval represented by the triangle.

My method of utilizing these known principles and geometric relations will be readily understood by referring to Fig. 2. I employ a flexible measuring element, wound upon a rotatable circular carrier, 5 The circular carrier is rotatively mounted on one traversing element, [0. The free end of the flexible measuring element is attached to the other traversing element, H.

The met od, briefly statec, is as follows: One end of a ile le measuring element is moved in a straight line, in a given direction (such as 0A) with a velocity at each moment proportional to the reactive power. Simultaneously, a circular carrier having the flexible measuring element wound about periphery is moved from the same starting point in a straight line (such as 013), at right angles to .e first, with a velocity at each moment proportional o the ei'lective power. At the expiration of a redeterznined interval of time, the two travers ng notions aforesaid are stopped; the amount of rotation of the circular carrier, due to withdrawal of the flexible element, is recorded; the ez-i nt of traverse of the carr'er is also recorded; and the carrier and free end of the flexible measuring element are quickly returned to the starting point (0 in Fig. 1). These operations are repeated for each succeeding time interval, so long as the records of interval demand are desired.

It wi be observed that the degree of rotation of the circular carrier is roportional to the separation of the stopping points (A and B of Fig. l) and is ereiore a measure of the apparent energy delivered during the time interval. The extent of traverse of the carrier is a measure of the effective energy for the time interval. During the return or the elements to zero position, the circular carrier is reversely rotated, to rewind the flexible element completely thereon.

As indicated in 2, the following features are comprised in a suitable means for performing this method rnechanically2-a first slider or traversing element i movable in the directions indicated by arrows in response to an effectiveenergy meter; a second slider or traversing element ii movable in the directions indicated by arrows ll in response to a reactive-energy meter (connected to measure wattless component); a circular carrier or drum i i rotatively mounted on slider 18; a small guide pulley 25 mounted on slider it; and a flexible measuring element 12, WOlllld upon the drum Ed, passing over the guide 15, and having its free end attached to the slider H at the point l3. The flexible measuring element may consist of a thread, or a thin metal tape, or may be of any other suitable form. The drum i4 is provided with a spring or other means to keep the measur ng element suiilciently taut and to rewind it during the rots-active movements of the traversing elements. At the beginning of each time interval, the points it and 15 on the respective sliders are both at the point of origin, 0. The angular motions of the drum may be transmitted to a non-return pointer of any suitable constructicn, so that the position of the pointer will show the largest angle passed over by the drum in any one or" the successive time intervals. Thus the pointer registers the maximum interval demand volt-amperes. Similarly, the rectilinear motions of the traversing element may be transmitted to another nonreturn pointer, which will show the greatest traverse of the element It! in any one of the successive intervals; the spy registering the maximum interval-demand in watts.

When it is desired to record the effects or" leading as well as lagging currents, the traversing element for measuring the reactive component will be arranged to move in one direction for lagging currents and in the opposite direction for leading currents.

Should it be desired to sum up the apparent energy delivered during an en ire billing period, this can be done by mounting, upon the traver ing member H], a standard registering train of gears of small dimensions; and operatively connecting th first gear of the train to the shaft E4 through a one-way clutch.

hi practice, the sliders t9 and l I are under the control or" a clock mechanism, being thereby automatically returned to their zero positions at the close of each time interval. For example, ii the time interval is to be fiftee minutes, the clock mechanism will be adjusted to return both sliders to zero four times per hour.

When it is desired to record each separate interval demand, with its time of occurrence, a movable paper chart is added to the clock mechanism. In Fig. 2, the edges of such a chart are diagrammatically indicated by the broken lines iii; the travel oi" the chart bei; in either of the directions indicated by the arrows lE. At the close of each time interval, before the sliders return to zero, a printing wheel in connection with drum is is caused to strike the paper and thereby to print a number or character representing the apparent-power demand (volt amperes). distance of this impression from a zero line 8 on the chart is measure of the effective-power demand (watts). By this means the mechanism makes a record of both the l;v.-a. demand and the kw. demand in one opera ion ior each successive time interval. A suitable time scale on the chart shows the time of day at which each demand occurred.

The invention is not limited to any particular kind or form of energy me be used either with single-phase meters or polymeters of standard construction.

An apparatus for automatically performing all the functions reviously mentioned is shown diagrammatically in Figs. 4 and In gen ral. it is immaterial whether the of the ClT'liltil carrier is is at right angles to line of traveme, as in Fig. 2, or parallel to it, as in Fig. 3.

The traversing member II has a rack l9 meshing with a pinion 2! which is slidably mounted on a splined shaft, or a square shaft, 23 (Fig. 5). The pinion is normally in engagement with the rack I8, being held in engagement by a spring 24. A stationary electro-magnet 25, when energized, acts upon an annular iron flange 27 of the pinion 2 I, to slide the pinion outwardly on shaft 23, against the restraining pressure of the spring 24, until the pinion 2i and rack l9 are disengaged. Fig. 5 shows the positions of the parts when the magnet 25 is energized.

Rigidly mounted on shaft 23, is a ratchet wheel 29 which engages with a restraining pawl 3i, mounted on a stationary support, and also with an actuating pawl 33 mounted on a lever 35. The lever 35 is operated by an electro-magnet 31, which is in circuit with a contact maker 39 and a source of electromotive force 43. The contact 39 is momentarily closed at each revolution of a rotating member 4| of the reactive-energy meter Z, thus energizing the magnet 31, advancing the The I It is intended to iii) source of electromotive force 43.

ratchet wheel 29 one.notch, and thereby advancing the traversing member I by adefin'itesmall amount.

The other traversing member, I 0, isggeared to a second traversing mechanism, 22, 26, 28, 30,22,

'34, 36, which is of the same construction and is similar in operation to thefirst traversing mecha nism above described. The second traversing mechanism is operated by electro-magnet. ;3B, which is in circuit with a contact maker 46 and The contact maker 46 is momentarily closed at each revolution of a rotating member 42 of the efiectiveenergy meter Y, thus advancing the ratchet wheel 30 one notch, and advancing the .member 16 by a definite small amount.

If preferred, the traversing pinion may be;dis-.

engaged from the rack by pulling it radially out of mesh (as in Fig. 6) instead of-sliding it axially (as in Fig. 5). wheel -9| is propelled by a lever 92wandpawl 94, operated by a plunger electro-magnet '91 which takes the place of magnet -38 in Fig. 3. The ratchet wheel 9| is rigidly attached to a gear wheel 66, coaxial with 9|, on a common shaft Behaving stationary bearings. A-tilting 'frame 85 fulcrumed on the axis 86, carries a gearor pinion 84 meshing permanently with gear 66. The pinion 24 is normally held inengagement with rack 26 on the traversing member I6 by meansof a spring 8'1. But a plunger magnet '88, which takes the place of magnet 26 in the circuit shown in Fig.

3, serves to tilt the frame 185, in opposition to spring 81, thereby disengaging thejpinion-84 from the rack 2!! whenever the magnet .88 isuenergized.

, Obviously a similar mechanism is applicable to p the traversing member II, for which purpose the pinion 84 replaces pinion 2|, magnet :91 replaces 31, and magnet 86 replaces 25in Fig. 3.

The magnets 25 and 26 are connected electrically in series with afirst contact-maker 44, a second contact maker 45, and-a source of electromotive force 43., Thecontactdevice 44 maybe of any suitable form adapted to'be closed'bya movable element 46 under control of a clockor constant-speed motor 5|. As shown in Fig. 3, the movable element may be a lever 46 fulcrumed at 41, and having an operating spring 48. The lever 46 carries a roller 49 which presses against a cam wheel 56 under the action of the spring 48. The cam wheel 56-is rotated by the timing mechanism 5| at a rate such as to closethe contact maker 44 at the expiration of each predetermined time interval.

The contact device 45 is operated by an auxiliary lever 52 fulcrumed at 53. A lug or arm 54 on the lever 46 is adapted to engage the lever 52 near its right-hand end, whereby to close the contact device 45. Another lug 55, on the traversing member I, is adapted to engage the lever 52 near its left-hand end, whereby to open the contact device 45.

The traversing member I has a projection 56 adapted to engage a catch element 51 on a dog 58 when near the limit of its retractive movement.

The dog 58 is pivoted at 59 and hangs normally with its catch element adjacent to the surface of the slider H; but it is provided with a. trigger element 66 adapted to be engaged by a projection Referring to Fig. 6, the ratchet The operation of :the traversing and restoring mechanism is as follows: At the beginning of a time interval, the lever-46 is in its uppermost position, and the contact device 44 is closed. Both traversing members are then at zero position.. The lug is in engagement with lever 52; and contact device45 is open. Therefore the magnets 25, 26, are on open circuit, and the pinions 2| 22, are engaged with theracks I9, 20. As time proceeds, the traversing members 16, H, are, moved forward by'the pinions, being drivenbyithe ratchet wheels 29, 30, in response to the meters .2, Y, aspreviously explained. Meanwhile the cam wheel 56 is being rotated by the timing mechanism, thus moving the roller 49 away from 'the cam center, depressing the lever '45,.against the force ofthe spring 48, and thereby opening the electrical contact 44. After 44 has opened, the arm 54 presses upon the switch lever 52, and continues to move its right hand end downward, thus closing contact 45. The magnets 25, 26, remain on open circuit because 44 was opened before 45 was closed.

At the termination of the time interval, as

determined by the timing mechanism 5|, the cam wheel 56, having made a complete revolution, releases the lever 46, which is then suddenly operated by the spring 48 to close the contact 44 and release lever 52 from engagement with arm 54. Contact 45 remains closed; and the closing of to complete its retractive movement, its projecting finger 6| strikes trigger 60, thus moving thecatch 57 away from member so that the projection 56 is free to pass the catch, and the member completes its retractive movement without interruption. On the other hand, if

member II is first, its projection 56 engages with the catch 57 and'itsmotion is thereby momentarily arrested, just short of its zero position. When member l0 reaches zero position,its projection 6| strikes and rests against triggerBIJ, thereby permitting member 'H to complete its stroke. The lug :55 on member engages the end of lever 52 at the moment that the projection 56 passes beyond the catch 51. The

remainder of the stroke of the member H is just suiiicient to operate the lever '52, and thereby to open the electrical contact 45. The lever 52 remains in either its up or down position by friction, being preferably provided with a friction spring for that purpose. The contacts at 45, as well as those at 44, are preferably of a sliding character, asqbetween clips and a blade, so that an appreciable movement of the lever, in each instance, is necessary to'open them.

Immediately upon the opening of contact 45, the magnets 25, 26, are de-energized, the pinions 2|, 22, are slipped into engagement with the racks by the'action of springs'24, and the forward motions of the traversing members begin again and continue through another time in terval as previously explained.

In Fig.3, the flexiblemeasuring element i2 is attached to traversing member H at point 13, passes over a small roller |5,'-and is wound about adrum|4 carried .by traversing member I6. The

drum I4 is secured on a shaft 64 which turns in suitable bearings. A spiral spring 85, interacting between the shaft 64 and the member 10, tends to Wind the flexible element [2 upon the drum, and serves to keep the flexible element taut.

The maximum interval demand for apparent power is registered by a non-return pointer 66. A circular scale 8?, preferably calibrated in kilovolt-arnperes, is fixed upon the traversing member it. The pointer t3 turns upon a suitable friction hub on the member Hi. The shaft 64 carries an arm having a pin 69 adapted to engage the pointer 66. The pointer is turned by pin 59 to a pos tion corresponding to the maximum angular displacement or" the arm 88, and remains in that position when the arm 68 is retracted.

It is obvious that the maximum interval demand for eiiective power can be registered by a non-return slidable pointer, 8i, arranged to slide on a stationary rod or track 82, in response to a pusher element 83, carried on the traversing member For service where it is desired to have a record of all the sen .ate interval demands, I add a printing wheel, record sheet and means for impressing the rec rds, as now to be explained. The printing wheel '59 is mounted on a shaft 54, to rotate with the drum i l. The record sheet or chart i8 is carried upon rollers '52, "93, of usual construction, propelled by the clock or constantspeed motor 55, through shaft 1'5 and gears 15, E6. Beneath the record sheet, and directly under the or lat ral travel or" the type wheel it, is a stamping platen or hammer 'il. This forms an extension of the lever 45, to which it is secured by a more flexible element or portion 78. When the lever is released by the cam wheel 50, the lever stikes a stop 19, bringing it abruptly to rest; but the portion '53 bends sufficiently to permit the platen l1, by virtue of its momentum, to strike a blow against the record sheet and type wheel. Carbon paper is ordinarily used to m ke the visible impression. Simultaneously i the striking of this blow of the platen against the type wheel, the magnets 25, 25, are energized through the contactor 4; by the time the impression has been made on the chart, the pinions 2S, are clearing the edges of the racks i9, 28; and immediately the traversing members return to zero position in the manner previously explained. The flexible element !2 is rewound upon the circular carrier M by the action of spring 6E.

During each time interval the clock advances the chart i8 a sufficient distance to present a fresh surface for the next record.

Obviously, the records of successive interval demands for eii'ective power may be rinted in the form of a dot or short line either by the printing wheel itself, or by a type fixed on the traversing member ii? adjacent to the printing wheel,

The constructions herein shown are to be understood illustrative only and not as defining the limits of the invention.

I claim:

1. The method of measin'ing time-interval demand for apparent power which comprises: moving an element from a giv n origin of motion in a first straight line with a velocity proportional to one of the components of apparent power; moving a point from said origin in a second straight line substantially at ri ht angles to said first line with a velocity proportional to the other component of apparent power; rotating said element in proportion to its distance from said point; stopping said motions at the expiration of the predetermined time interval; and denoting the interval demand by the degree of rotation of said element.

2. The method of measuring and denoting in one distinctive reference the apparent and ei fective power demands in a predetermined time interval, by: giving rectilinear motion to a point from a given origin in proportion to reactive power; transporting a rotative element from said origi in a straight line at right angles to said rectilinear motion in proportion to effective power; rotating said rotative element in proportion to its distance from said moving point; and, at the expiration of the time interval, denoting the aforesaid interval demands respectively by the degree of rotation of said rotative element, and its distance from said origin.

3. Means for measi ing and denoting the magnitude of a vector difference comprising: a rotatable circular carrier; a flexible element adapted at one end to cause rotation of said carrier and having the other end free; means for transporting said carrier from a given origin in proportion to a first vector quantity; and means for moving the free end or said flexible element, from said origin, in proportion to a second vector quantity; whereby to d note said first and second quantities by the directions and distances of said carrier and free end from said origin, and the magnitude of their vector difference by the amount of rotation of said carrier.

4. A first traversing element movable along a first straight line from a given starting point; a second traversing element movable from said starting point along a second straight line; a flexible measuring element responsive to said traversing elements; means for keeping said flexible measuring element taut in the plane common to said straight lines; and a rotative element on one of said traversing elements responsive to said flexible measuring element.

5. In an instrument of the class described, the combination of first and second traversing elements constrained to recurrent rectilinear motions in a common plane in paths substantially at right angles; a rotative element mounted on one of said traversing elements, to travel in a straight line therewith; and a flexible measurmg element attached to the other traversing element and adapted to produce rotation of said rotative element.

6. In an instrument of the class described, in combination with two traversing elements constrained to rectilinear motions in divergent paths; a flexible measuring element; and a printing wheel subject to translation in response to one of said traversing elements and subject to rotation in response to said flexible measuring element.

'7. A spring-controlled winding element carried by one of two straight-line traversing elements and adapted to imprint a record of the resultant of separate movements of said two traversing elements.

8. A printing wheel carried upon a first straight-line traversing member and rotatively responsive to a flexible measuring element in operative relation with a second traversing memher.

9. In a measuring instrument the combination of: a flexible measuring element responsive at one end to a first quantity; and a circular printing element rotative in response to said flexible measuring element while subject to straight-line traversing movements in response to a second quantity.

10. In an instrument for recording successive time-interval demands for apparent power, the combination of: first and second traversing members constrained to straight-line paths at right angles; a flexible measuring element havone interval demands for apparent power and effective power: a pair of traversing members mov-, able in divergent rectilinear paths in a common plane; a winding element rotatively mounted on one of said traversing members and thereby subjected to movements of translation; a flexible measuring element movable in said plane in response to said traversing members and adapted to turn said winding element; a record sheet movable crosswise of the path of translation of said winding element; and means for making an imprint on said record sheetat the expiration of each time interval whereby to record the degree of angular deflection and the extent of linear traverse of said winding element.

12. The combination of: a traversing member; s,

a rotative element carried by said traversing member; a movable chart having a longitudinal reference line; and printing means adapted to print upon said chart a mark denoting the degree of rotation of said rotative element, at a distance from said reference line denoting the ex tent of traverse of said traversing member.

I 13. In an instrument of the class described; the combination of: a pair of traversing elements; a flexible measuring element; a rotative element on one of said traversing elements; traversing means adapted recurrently to advance said traversing elements; restoring means adapted to retract said traversing elements; timing means; a movable record sheet; and a printing wheel responsive to said flexible measuring element in operative relation with said record sheet and said timing means.

14. In an instrument of the class described, in conjunction with a meter, a timing device and a traversing member: a wheel responsive to said meter; a shaft secured to said wheel; a pinion slidably mounted on said shaft; a rack on said traversing member adapted to mesh with said pinion; a spring adapted to slide said pinion inwardly on said shaft to engage with said rack; and means responsive to said timing device to slide said pinion outwardly on said shaft to disengage said rack.

15. In conjunction with a pair of meters and first and second traversing members: racks on said traversing members; pinions responsive to said meters and adapted to recurrently engage said racks; a timing means; means for disengaging said pinions from said racks in response to said timing means; means for insuring complete retraction of the first traversing member in advance of the second traversing member; and means responsive to the second traversing member for engaging said pinions with said racks.

16. In combination: a timing mechanism; a printing element; a pair of traversing members having racks; pinions adapted to recurrently engage with said racks; a recording chart; a movable element responsive to the timing mechanism and cooperative with said printing element to impress records upon said chart; means responsive to said movable element to disengage said pinions from said racks; and means responsive to the traversing members to engage said pinions with said racks.

17. In combination with a timing mechanism and a pair of traversing members: forwarding means, for advancing said traversing members; electrical means for disengaging said forwarding means; a movable element responsive to the timing mechanism; a first electrical contact device responsive to said movable element and in circuit with said electrical means; a second electrical contact device in circuit with said electrical means; and means responsive to said movable element to close said second contact device, and responsive to one of said traversing members to open said second contact device.

18. The combination of: first and second traversing members; a detent adapted to arrest the retractive movement of the first traversing member; a projecting element on said first traversing member adapted to engage said detent; and means on said second traversing mem-' ber adapted to shift said detent out of the path of travel of said projecting element; whereby to insure complete retraction of said second traversing member before the retraction of said first traversing member can be completed.

' ALEXANDER DAWES DU BOIS. 

